Object and sequence number management

ABSTRACT

Techniques are provided for orphan object detection, invalid sequence number detection, and asynchronous object cleanup. A storage system may store data within one or more tiers of storage, such as a storage tier (e.g., solid state storage and disks maintained by the storage system), a remote object store (e.g., storage provided by a third party storage provider), and/or other storage tiers. Orphan objects, within the remote object store, that are no longer used by the storage system may be detected and/or deleted. When an aggregate of volumes is deleted, corresponding objects, within the remote object store, may be identified and/or deleted. Invalid sequence numbers (e.g., lost or corrupt sequence numbers locally maintained in a metafile) assigned to objects within the remote object store may be identified, deleted, and/or fixed.

RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S.application Ser. No. 15/581,447, filed on Apr. 28, 2017, now allowed,titled “OBJECT AND SEQUENCE NUMBER MANAGEMENT,” which is incorporatedherein by reference.

BACKGROUND

Many storage systems may provide clients with access to data storedwithin a plurality of storage devices. For example, a storage controllermay store client data within a set of storage devices that are locallyaccessible (e.g., locally attached to the storage controller) orremotely accessible (e.g., accessible over a network). A storageaggregate (e.g., a composite aggregate comprising a set of volumes) ofstorage may be generated from the set of storage devices (e.g., thestorage aggregate may be stored across one or more storage devices). Thestorage aggregate may be exported from a storage file system to aclient. The storage aggregate may appear as one or more storagecontainers to the client, such as a volume or logical unit number (lun).In this way, the storage aggregate abstracts away the details, from theclient, of how the storage aggregate is physically stored amongst theset of storage devices.

Some storage systems may store data within a multi-tiered storagearrangement. For example, the storage controller may store data within ahard disk drive tier and a solid state storage tier. The hard disk drivetier may be used as a capacity tier to store client data and forprocessing input/output operations. The solid state storage tier may beused as a cache for accelerating the processing of storage operations.Different storage tiers have different characteristics and behaviors,which can affect performance and guarantees provided to clients by astorage system.

In an example, a storage system may utilize a storage tier (e.g., alocal storage tier hosted, owned, and/or managed by one or more nodes ofa storage environment associated with the storage system) and a remoteobject store as two of the storage tiers within which the storage systemstores data. The storage system may be able to provide highavailability, security, data consistency, data protection, and/or otherguarantees using the storage tier because the storage system may manageand control the storage tier. However, the storage system may be unableto provide similar guarantees, such as that data is properly stored,managed, is consistent, and is accurate, to clients for the remoteobject store because the storage system does not manage and control theremote object store (e.g., a third party provider may host and managethe remote object store). For example, new data could be written to aremote third party object store. When reading the new data, old data orno data could be returned by the remote third party object store due todelay. In another example, local operations such as deleting anaggregate may be quick and efficient to locally implement for thestorage tier, while identifying and deleting corresponding objectswithin the remote third party object store may be slow and delaycompletion of deleting the aggregate. Thus, the storage system may beunable to provide the same level of enterprise guarantees andefficiencies when working with the remote third party object store asbackend storage.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of asynchronousobject cleanup.

FIG. 4 is a component block diagram illustrating an exemplary computingdevice for asynchronous object cleanup.

FIG. 5 is a flow chart illustrating an exemplary method of orphan objectdetection.

FIG. 6 is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where a volume moveoperation is performed.

FIG. 7 is a flow chart illustrating an exemplary method of invalidsequence number detection.

FIG. 8 is a component block diagram illustrating an exemplary computingdevice for invalid sequence number detection.

FIG. 9 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more techniques and/or computing devices for orphan objectdetection, invalid sequence number detection, and asynchronous objectcleanup are provided herein. A storage system may utilize multiple tiersof storage to store client data. For example, the storage system mayutilize a storage tier (e.g., a performance storage tier, such as asolid state storage tier or a hard disk drive storage tier, locallyhosted and/or maintained by nodes of a storage environment associatedwith the storage system), a remote object store (e.g., a distributednetwork of storage provided by a third party provider, cloud storage,etc.), and/or other tiers of storage. The storage system may create acomposite aggregate of volumes using storage within the storage tier andthe remote object store. For example, more frequently accessed or morerecently accessed data may be stored within the storage tier because thestorage tier may have lower latency than the remote object store. Lessfrequently accessed or less recently accessed data may be stored withinobjects maintained by the remote object store.

When the storage system receives a delete request to delete thecomposite aggregate, data of the volumes of the aggregate must bedeleted from the storage tier and objects belonging to the volumes mustbe deleted from the remote object store. Deleting the data from thestorage tier (e.g., from solid state drives, hard disk drives, and/orother storage devices hosted by the storage system) may be quick andefficient. Unfortunately, deleting objects from the remote object store,which may be hosted by a third party provider, may be time consuming andinefficient because objects corresponding to the volumes must beidentified and delete operations must be issued to the remote objectstore for the objects. Such delays can be disruptive to clients becausestorage of the storage tier may be unavailable until the objects aredeleted from the remote object store. Another issue is where staleobjects, not referenced or used by the storage system, may remain withinthe remote object store. Thus, a client may be charged for storing staledata within the remote object store.

Accordingly, as provided herein, data, associated with a compositeaggregate that is to be deleted, is deleted from a storage tier (e.g.,storage hosted or managed by nodes associated with a storage system) inresponse to receiving a delete request for the composite aggregate. Thedata is deleted without waiting for corresponding objects of thecomposite aggregate to be deleted from a remote object store (e.g.,storage hosted or managed by a third party provider such as a cloudstorage provider). An asynchronous object cleanup operation is performed(e.g., at a later point in time after the data is deleted from thestorage tier and such storage space is freed up, such as after thedelete request is acknowledged back to a requestor such as a client ascomplete) to delete the corresponding objects from the remote objectstore. In this way, storage of the storage tier may be freed up andavailable before the asynchronous object cleanup operation is initiatedor completes. In another embodiment, orphan objects that are no longerreferenced or used by the storage system (e.g., no longer referenced byany volumes of the composite aggregate) may be identified and deletedfrom the remote object store. In another embodiment, invalid sequencenumbers used to reference objects may be identified, deleted, and/orrepaired.

To provide for orphan object detection, invalid sequence numberdetection, and asynchronous object cleanup, FIG. 1 illustrates anembodiment of a clustered network environment 100 or a network storageenvironment. It may be appreciated, however, that the techniques, etc.described herein may be implemented within the clustered networkenvironment 100, a non-cluster network environment, and/or a variety ofother computing environments, such as a desktop computing environment.That is, the instant disclosure, including the scope of the appendedclaims, is not meant to be limited to the examples provided herein. Itwill be appreciated that where the same or similar components, elements,features, items, modules, etc. are illustrated in later figures but werepreviously discussed with regard to prior figures, that a similar (e.g.,redundant) discussion of the same may be omitted when describing thesubsequent figures (e.g., for purposes of simplicity and ease ofunderstanding).

FIG. 1 is a block diagram illustrating the clustered network environment100 that may implement at least some embodiments of the techniquesand/or systems described herein. The clustered network environment 100comprises data storage systems 102 and 104 that are coupled over acluster fabric 106, such as a computing network embodied as a privateInfiniband, Fibre Channel (FC), or Ethernet network facilitatingcommunication between the data storage systems 102 and 104 (and one ormore modules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1, that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets, a Storage Area Network (SAN) protocol, such as Small ComputerSystem Interface (SCSI) or Fiber Channel Protocol (FCP), an objectprotocol, such as S3, etc. Illustratively, the host devices 108, 110 maybe general-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more storagenetwork connections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, cloud storage (e.g., a storage endpoint may bestored within a data cloud), etc., for example. Such a node in theclustered network environment 100 can be a device attached to thenetwork as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the clustered network environment 100, nodes 116, 118can comprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise network modules 120, 122 and disk modules 124, 126. Networkmodules 120, 122 can be configured to allow the nodes 116, 118 (e.g.,network storage controllers) to connect with host devices 108, 110 overthe storage network connections 112, 114, for example, allowing the hostdevices 108, 110 to access data stored in the distributed storagesystem. Further, the network modules 120, 122 can provide connectionswith one or more other components through the cluster fabric 106. Forexample, in FIG. 1, the network module 120 of node 116 can access asecond data storage device by sending a request through the disk module126 of node 118.

Disk modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, disk modules 124, 126 communicate with the data storage devices128, 130 according to the SAN protocol, such as SCSI or FCP, forexample. Thus, as seen from an operating system on nodes 116, 118, thedata storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the clustered network environment100 illustrates an equal number of network and disk modules, otherembodiments may comprise a differing number of these modules. Forexample, there may be a plurality of network and disk modulesinterconnected in a cluster that does not have a one-to-onecorrespondence between the network and disk modules. That is, differentnodes can have a different number of network and disk modules, and thesame node can have a different number of network modules than diskmodules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the storage networking connections 112, 114. As anexample, respective host devices 108, 110 that are networked to acluster may request services (e.g., exchanging of information in theform of data packets) of nodes 116, 118 in the cluster, and the nodes116, 118 can return results of the requested services to the hostdevices 108, 110. In one embodiment, the host devices 108, 110 canexchange information with the network modules 120, 122 residing in thenodes 116, 118 (e.g., network hosts) in the data storage systems 102,104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. In an example, a disk array can include alltraditional hard drives, all flash drives, or a combination oftraditional hard drives and flash drives. Volumes can span a portion ofa disk, a collection of disks, or portions of disks, for example, andtypically define an overall logical arrangement of file storage on diskspace in the storage system. In one embodiment a volume can comprisestored data as one or more files that reside in a hierarchical directorystructure within the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the clustered network environment 100, the host devices 108, 110 canutilize the data storage systems 102, 104 to store and retrieve datafrom the volumes 132. In this embodiment, for example, the host device108 can send data packets to the network module 120 in the node 116within data storage system 102. The node 116 can forward the data to thedata storage device 128 using the disk module 124, where the datastorage device 128 comprises volume 132A. In this way, in this example,the host device can access the volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the storage networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the network module 122 in the node 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The node 118 can forward the data to the data storagedevice 130 using the disk module 126, thereby accessing volume 1328associated with the data storage device 130.

It may be appreciated that orphan object detection, invalid sequencenumber detection, and asynchronous object cleanup may be implementedwithin the clustered network environment 100. In an example, the node108 and/or the node 118 may utilize a remote object store and/or thedata storage devices 128, 130 for serving client requests. It may beappreciated that orphan object detection, invalid sequence numberdetection, and asynchronous object cleanup may be implemented for and/orbetween any type of computing environment, and may be transferablebetween physical devices (e.g., node 116, node 118, a desktop computer,a tablet, a laptop, a wearable device, a mobile device, a storagedevice, a server, etc.) and/or a cloud computing environment (e.g.,remote to the clustered network environment 100).

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The data storage system 200 comprises a node202 (e.g., nodes 116, 118 in FIG. 1), and a data storage device 234(e.g., data storage devices 128, 130 in FIG. 1). The node 202 may be ageneral purpose computer, for example, or some other computing deviceparticularly configured to operate as a storage server. A host device205 (e.g., 108, 110 in FIG. 1) can be connected to the node 202 over anetwork 216, for example, to provide access to files and/or other datastored on the data storage device 234. In an example, the node 202comprises a storage controller that provides client devices, such as thehost device 205, with access to data stored within data storage device234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The data storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1). Thus, the node 202, such as a network storagecontroller, can respond to host device requests to manage data on thedata storage device 234 (e.g., or additional clustered devices) inaccordance with these host device requests. The operating system 208 canoften establish one or more file systems on the data storage system 200,where a file system can include software code and data structures thatimplement a persistent hierarchical namespace of files and directories,for example. As an example, when a new data storage device (not shown)is added to a clustered network system, the operating system 208 isinformed where, in an existing directory tree, new files associated withthe new data storage device are to be stored. This is often referred toas “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software application code and datastructures. The processors 204 and adapters 210, 212, 214 may, forexample, include processing elements and/or logic circuitry configuredto execute the software code and manipulate the data structures. Theoperating system 208, portions of which are typically resident in thememory 206 and executed by the processing elements, functionallyorganizes the storage system by, among other things, invoking storageoperations in support of a file service implemented by the storagesystem. It will be apparent to those skilled in the art that otherprocessing and memory mechanisms, including various computer readablemedia, may be used for storing and/or executing application instructionspertaining to the techniques described herein. For example, theoperating system can also utilize one or more control files (not shown)to aid in the provisioning of virtual machines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a network 216, which may comprise, among otherthings, a point-to-point connection or a shared medium, such as a localarea network. The host device 205 (e.g., 108, 110 of FIG. 1) may be ageneral-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network 216 (and/or returned to anothernode attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on disk arrays 218, 220, 222can be implemented as one or more storage volumes 230, 232 that arecomprised of a cluster of disks 224, 226, 228 defining an overalllogical arrangement of disk space. The disks 224, 226, 228 that compriseone or more volumes are typically organized as one or more groups ofRAIDs. As an example, volume 230 comprises an aggregate of disk arrays218 and 220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, Qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the one or more LUNs 238.

It may be appreciated that orphan object detection, invalid sequencenumber detection, and asynchronous object cleanup may be implemented forthe data storage system 200. In an example, the node 202 may utilize aremote object store for serving client requests. It may be appreciatedthat orphan object detection, invalid sequence number detection, andasynchronous object cleanup may be implemented for and/or between anytype of computing environment, and may be transferrable between physicaldevices (e.g., node 202, host device 205, a desktop computer, a tablet,a laptop, a wearable device, a mobile device, a storage device, aserver, etc.) and/or a cloud computing environment (e.g., remote to thenode 202 and/or the host device 205).

One embodiment of asynchronous object cleanup is illustrated by anexemplary method 300 of FIG. 3. A storage system may provide clientswith access to client data stored within a backend. The backend may beconfigured with one or more tiers of storage. For example, the backendmay be configured with a storage tier (e.g., solid state drives, harddisk drives, etc.), a remote object store (e.g., a third party storageprovider, cloud storage, etc.), etc. The storage system may store datawithin the storage tier as a performance tier for frequently or recentlyaccessed data because the storage tier may have lower latency and moreguarantees than the remote object store tier. The storage system maymigrate data from the storage tier to the remote object store (e.g.,less frequently or less recently accessed data) or may store new data tothe remote object store.

The storage system may create a composite aggregate composed of a set ofvolumes that are exposed to clients. Data of the set of volumes may bestored within the storage tier and within objects of the remote objectstore. An object may be assigned a name based upon a volume identifierof a volume, of the composite aggregate, to which the object belongs.For example, a prefix of the name may be derived from the volumeidentifier. The name may also be derived from a sequence number uniquelyassigned to the object. For example, the prefix of the name may bederived from the sequence number. Monotonically increasing sequencenumbers may be assigned to objects that are created within the remoteobject store for a volume. In an example, the name of the object may bederived from a hash for the volume identifier and/or the sequencenumber.

The storage system may store objects within the remote object store. Anobject may comprise a header. The header may comprise a version of theobject, an indicator as to whether the object is encrypted, a creationtimestamp for the object, a volume identifier (e.g., a buff treeuniversal identifier such as a buftree-uuid), an identifier of a name ofthe object (e.g., a hash of the name and the buftree-uuid, which can beread back after a put operation of the object into the remote objectstore to verify the hash), and/or other information. In one example, theheader is 32 bytes or any other size of information.

The object may comprise one or more object pages corresponding to datachunks, such as data chunks derived from data moved from the storagetier (e.g., a performance storage tier, such as a solid state storagetier or a disk storage tier) of the storage system to the remote objectstore. In one example, the object may comprise space for 1024 objectpages, such as a first object page, a second object page, and/or otherobject pages. The first object page may comprise a first data chunk(e.g., 4 kilobytes of data or any other size of data) and a firstcontext associated with the first object page.

The first context may comprise an indicator as to whether the object isencrypted. The first context may comprise an encryption key index usedto identify an encryption key. The first context may comprise apseudobad indicator to indicate whether data read from the local storagetier had an error such as a disk error and the data content in theobject is inconsistent. The first context may comprise an indicator asto whether a RAID or storage OS marked the pseudobad error. The firstcontext may comprise an unverified error indicator to indicate that whendata read from the local storage tier resulted in an unverified RAIDerror. The first context may comprise a wrecked indicator that is setwhen data is forcefully corrupted. The first context may comprise a fileblock number (e.g., a location of the file block number for the firstdata chunk within the first volume). The first context may comprise achecksum for the first data chunk and the first context. In an example,the first context may comprise 16 bytes of information or any other sizeof information.

At 302, a delete request to delete the composite aggregate may bereceived such as by the storage system. At 304, data, associated withthe composite aggregate, may be deleted from a storage tier (e.g., alocal storage tier hosted and/or managed by nodes of a storageenvironment associated with the storage system, such as hard disk drivesand/or solid state drives). In this way, storage space of the storagetier may become available such as for client access and data storage(e.g., before all corresponding objects are deleted from the remoteobject store).

At 306, an asynchronous object cleanup operation may be performed. Inone example, the data within the storage tier may be deleted and thefreed storage space may be available to clients irrespective of whetherthe asynchronous object cleanup operation has been initiated or hascompleted. At 308, a list of volume identifiers for the set of volumescomprised within the composite aggregate may be obtained. For example,each volume may be assigned its own unique volume identifier. In anexample, these volume identifiers may be stored within a cluster-widedatabase (e.g., an rbd database) that is accessible to a plurality ofnodes of a storage environment (e.g., the storage system). The storageenvironment, associated with the storage system, may host and/or managethe storage tier, while a third party provider may host and/or managethe remote object store. In another example, nodes of clusters of thestorage environment may be queried for volume identifiers of volumescurrently managed by the nodes.

At 310, for each volume identifier within the list of volumeidentifiers, a request may be sent to the remote object store for a listof object names of objects having names associated with a volumeidentifier, at 312. These objects are associated with a volume assignedthe volume identifier because objects are named based upon a volumeidentifier of a volume to which an object belongs. At 314, the list ofobject names are received from the remote object store (e.g., a list ofnames of objects that are assigned to the volume, having the volumeidentifier, of the composite aggregate that was deleted). At 316, deletecommands are issued to the remote object store to delete objects havingobject names within the list of object names. In this way, objectsassociated with the volume of the deleted composite aggregate aredelete. The list of volume identifiers are looped through so thatobjects of each volume of the deleted composite aggregate are deletedfrom the remote object store. Because the composite aggregate has beendeleted and corresponding objects have been deleted from the remoteobject store, the list of volume identifiers can be deleted from thecluster-wide database.

FIG. 4 illustrates an example of a system 400 for asynchronous objectcleanup. A storage system 404 may host and/or manage a storage tier 414(e.g., storage locally accessible to one or more nodes of one or moreclusters associated with the storage system). The storage system 404 maystore data within the storage tier 414, such as client data. The storagesystem 404 may also store data within objects 418 of a remote objectstore 416 (e.g., storage provided by a third party storage provider).The storage system 404 may maintain a metafile 406 comprisinginformation related to the objects 418, such as sequence numbersassigned to objects of a volume and a mapping between an object ID(e.g., file system tree pointers point to the object ID and an offsetwithin the object) and an object name. The storage system 404 maymaintain a composite aggregate 412 composed of a set of volumes that areexposed to clients.

The storage system 404 may receive a delete request 402 to delete thecomposite aggregate 412. The storage system 404 may delete dataassociated with the composite aggregate 412 (e.g., data of the set ofvolumes) from the storage tier 414 so that storage space is quickly andefficiently freed up for use. In one example, the storage space may bemade available and/or the delete request 402 may be acknowledged ascomplete to a requestor (e.g., a client) before all correspondingobjects of the composite aggregate 412 are deleted from the remoteobject store 416.

The storage system 404 may subsequently perform an asynchronous objectcleanup of objects comprising data of the composite aggregate 412 inorder to delete such objects from the remote object store 416. Thestorage system 404 may obtain a list of volume identifiers 408 for theset of volumes of the composite aggregate 412 that was deleted. For eachvolume identifier within the list of volume identifiers 408, a request420 is sent to the remote object store 416 for a list of object names410 of objects that have names associated with a volume identifier.These objects are identified by their object names as belonging to avolume, of the composite aggregate 412, assigned the volume identifierbecause the volume identifier of the volume to which the object belongsis used to generate an object name for an object. In this way, thestorage system 404 issues delete commands to the remote object store 416to delete objects having object names within the list of object names410. In this way, the list of volume identifiers 408 are looped throughto identify and delete objects from the remote object store 416 that areassociated with the composite aggregate 412 that was deleted.

One embodiment of orphan object detection is illustrated by an exemplarymethod 500 of FIG. 5. A storage system may provide clients with accessto client data stored within a backend. The backend may be configuredwith one or more tiers of storage. For example, the backend may beconfigured with a storage tier (e.g., solid state drives, hard diskdrives, etc.), a remote object store (e.g., a third party storageprovider, cloud storage, etc.), etc. The storage system may store datawithin the storage tier as a performance tier for frequently or recentlyaccessed data because the local storage tier may have lower latency andmore guarantees than the remote object store tier. The storage systemmay migrate data from the storage tier to the remote object store (e.g.,less frequently or less recently accessed data) or may store new data tothe remote object store.

The storage system may create a composite aggregate composed of a set ofvolumes that are exposed to clients. Data of the set of volumes may bestored within the storage tier and within objects of the remote objectstore. An object may be assigned a name based upon a volume identifierof a volume, of the composite aggregate, to which the object belongs.For example, a prefix of the name may be derived from the volumeidentifier. The name may also be derived from a sequence number uniquelyassigned to the object. For example, the prefix of the name may bederived from the sequence number. Monotonically increasing sequencenumbers may be assigned to objects that are created within the remoteobject store for a volume. In an example, the name of the object may bederived from a hash for the volume identifier and/or the sequencenumber.

When an object is no longer referenced or used by at least one volume orcomposite aggregate, then the object is an orphan object that comprisesstale data wasting storage space of the remote object store (e.g.,wasted storage space that a client may be paying for to a third partyprovider of the remote object store). Accordingly, it may beadvantageous to detect and address orphan objects.

At 502, a list of volume identifiers of volumes belonging to compositeaggregates of a storage environment may be obtained. For example, nodesof clusters of the storage environment may be queried for volumeidentifiers of volumes currently managed by the nodes. At 504, a requestmay be sent to the remote object store for a list of object names ofobjects maintained by the remote object store for the storageenvironment. In an example, batch requests for portions of the list ofobject names may be sent to the remote object store (e.g., a first batchcommand for a first portion of the list of object names such as 1000object names; a second batch command for a second portion of the list ofobject names such as a second 1000 object names; etc.). In this way, thelist of object names may be acquired from the remote object store.

At 506, for each object name within the list of object names, adetermination is made as to whether an object name matches a volumeidentifier within the list of volume identifiers, at 508. If the objectname matches the volume identifier, then an object having the objectname is determined to be a valid object that is used by a volume, of acomposite aggregate, assigned the volume identifier because the objectname is derived from the volume identifier, at 510. If the object namedoes not match any volume identifiers, then the object having the objectname is determined to be an orphan object that is not used by anyvolumes of the composite aggregates, at 512.

At 514, an orphan object list of orphan objects determined from the listof object names may be determined and/or displayed such as through auser interface. An orphan volume identifier list of volume identifiersof volumes to which the orphan objects belong may be determined and/ordisplayed such as through the user interface. Orphan volume identifierscan be identified from object names of orphan objects because objectnames are derived from volume identifiers of volumes to which objectsbelong.

In an example, a delete command may be received, such as through theuser interface, to delete a particular orphan object from the remoteobject store since no volumes use or reference that orphan object.Accordingly, a delete operation is sent to the remote object store todelete the orphan object. In another example, a delete all command maybe received, such as through the user interface, to delete orphanobjects associated with a particular volume identifier. Accordingly,delete operations are sent to the remote object store to delete theorphan objects associated with the volume identifier. In anotherexample, a delete all command may be received, such as through the userinterface, to delete all orphan objects within the orphan object list.Accordingly, delete operations are sent to the remote object store todelete the orphan objects within the orphan object list. In anotherexample, a command may be received from a requestor, such as through theuser interface, to retrieve data from an orphan object. Accordingly, theorphan object may be retrieved from the remote object store and datafrom the orphan object may be provided to the requestor.

FIG. 6 illustrates an example of a system 600 for orphan objectdetection. A storage system 602 may host and/or manage a storage tier(e.g., storage locally accessible to one or more nodes of one or moreclusters associated with the storage system). The storage system 602 maystore data within the storage tier, such as client data. The storagesystem 602 may also store data within objects 614 of a remote objectstore 612 (e.g., storage provided by a third party storage provider).The storage system 602 may maintain a metafile 604 comprisinginformation related to the objects 614, such as sequence numbersassigned to objects of a volume. The storage system 602 may maintain acomposite aggregate composed of a set of volumes that are exposed toclients.

Because the remote object store 612 may end up storing stale orphanobjects (e.g., due to corruption of the metafile 604 where an object isno longer referenced, due to no more volumes or other storage structuresreferencing or using data within an object, etc.), orphan objectdetection may be implemented. A list of volume identifiers 606 ofvolumes belonging to composite aggregates of a storage environmentassociated with the storage system 602 may be obtained. A request 610may be sent to the remote object store 612 for a list of object names608 of objects maintained by the remote object store 612 for the storageenvironment. For each object name within the list of object names 608, adetermination is made as to whether an object name of an object matchesany volume identifier within the list of volume identifiers 606. If theobject name of the object matches a volume identifier within the list ofvolume identifiers 606, then the object is determined as a valid objectbelonging to a volume having the volume identifier (e.g., the objectcomprises data associated with at least one volume). If the object namedoes not match any volume identifiers within the list of volumeidentifiers 606, then the object is determined as an orphan object thatdoes not belong to any volumes. In this way, an orphan object list 616and/or an orphan volume identifier list 618 (e.g., volume identifiers oforphan objects) may be determined and/or provided/displayed.

One embodiment of invalid sequence number detection is illustrated by anexemplary method 700 of FIG. 7. A storage system may provide clientswith access to client data stored within a backend. The backend may beconfigured with one or more tiers of storage. For example, the backendmay be configured with a storage tier (e.g., solid state drives, harddisk drives, etc.), a remote object store (e.g., a third party storageprovider, cloud storage, etc.), etc. The storage system may store datawithin the storage tier as a performance tier for frequently or recentlyaccessed data because the local storage tier may have lower latency andmore guarantees than the remote object store tier. The storage systemmay migrate data from the storage tier to the remote object store (e.g.,less frequently or less recently accessed data) or may store new data tothe remote object store.

The storage system may create a composite aggregate composed of a set ofvolumes that are exposed to clients. Data of the set of volumes may bestored within the storage tier and within objects of the remote objectstore. An object may be assigned a name based upon a volume identifierof a volume, of the composite aggregate, to which the object belongs.For example, a prefix of the name may be derived from the volumeidentifier. The name may also be derived from a sequence number uniquelyassigned to the object. For example, the prefix of the name may bederived from the sequence number. Monotonically increasing sequencenumbers may be assigned to objects that are created within the remoteobject store for a volume. In an example, the name of the object may bederived from a hash for the volume identifier and/or the sequencenumber. Sequence numbers of objects may be stored within a metafile usedto store information relating to objects stored within the remote objectstore such as a mapping between an object ID (e.g., file system treepointers point to the object ID and an offset within the object) and anobject name.

Unfortunately, a sequence number can become lost or corrupt from withinthe metafile. Accordingly, as provided herein, invalid sequence numbersare detected. At 702, a list of sequence numbers specified within themetafile are obtained. At 704, a request may be sent to the remoteobject store for a list of object names of objects having names derivedfrom sequence numbers monotonically assigned to such objects. In thisway, the list of object names may be acquired from the remote objectstore.

Sequence numbers are unique for a particular volume identifier of aparticular volume (e.g., sequence numbers are not unique across buftreeUUlDs but only within). In an example where the volume identifiercomprises a buftree UUID of XX, a storage file system knows aboutobjects XX-1, XX-2, XX-4, and XX-7 where 1, 2, 4, and 7 are sequencenumbers for the buftree UUID of XX. Orphan object detection may beperformed to determine whether there are other unknown objects for thebuftree UUID of XX such as XX-9. In an example, if the remote objectstore has an object with YY-8 where YY is a buftree UUID and 8 is asequence number, then sequences numbers for the buftree UUID of YY maybe evaluated to see if there is a YY-8. If not, then the object is anorphan object.

At 706, for each object name within the list of object names, adetermination is made as to whether a sequence number within a name ofan object matches any sequence numbers within the list of sequencenumbers, at 708. If the sequence number matches a target sequence numberwithin the list of sequence numbers, then the sequence number isdetermined to be valid, at 710. If the sequence number does not matchany sequence numbers within the list of sequence number, then thesequence number is determined to be invalid (e.g., lost or corrupt fromwithin the metafile, and thus an object assigned the sequence number maybe unidentifiable from the metafile for access from the remote objectstore such as for servicing client requests using data within theobject). In an example, the metafile may be determined, based upon thesequence number being invalid, to be corrupt where the sequence numberhas been lost or corrupted from within the metafile.

In an example, an indicator that the sequence number is invalid may bedisplayed such as through a user interface. In another example, thesequence number may be inserted back into the metafile. In anotherexample, a command may be received from a requestor to retrieve datafrom the object associated with the sequence number that is invalid.Accordingly, the object may be retrieved from the remote object store,and data of the object may be provided to the requestor.

FIG. 8 illustrates an example of a system 800 for invalid sequencenumber detection. A storage system 802 may host and/or manage a storagetier (e.g., storage locally accessible to one or more nodes of one ormore clusters associated with the storage system). The storage system802 may store data within the storage tier, such as client data. Thestorage system 802 may also store data within objects 814 of a remoteobject store 12 (e.g., storage provided by a third party storageprovider). The storage system 802 may maintain a metafile 804 comprisinginformation related to the objects 814, such as sequence numbersassigned to objects of a volume. The storage system 802 may maintain acomposite aggregate composed of a set of volumes that are exposed toclients.

Because the sequence numbers may become lost or corrupt within themetafile 804 (referred to as invalid sequence numbers), invalid sequencenumber detection may be implemented. The storage system 802 may obtain alist of sequence numbers 806 specified within the metafile 804. Eachobject within the remote object store 812 may be assigned a uniquesequence number. An object name of an object may be derived from asequence number assigned to the object. The storage system 802 may senda request 810 to the remote object store for a list of object names 808of objects maintained by the remote object store 812 for the storagesystem 802. In this way, the list of object names 808 are obtained fromthe remote object store 812.

The storage system 802 may loop through each object name within the listof object names 808 to identify invalid sequence numbers. In particular,for each object name within the list of object names 808, adetermination is made as to whether a sequence number within a name ofan object matches any sequence number within the list of sequencenumbers 806. If the sequence number matches a target sequence numberwithin the list of sequence numbers 806, then the sequence number isdetermined to be valid. If the sequence number does not match anysequence number within the list of sequence numbers 806, then thesequence number is determined to be an invalid sequence number 816 thathas been lost or corrupted within the metafile 804.

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 9, wherein the implementation 900comprises a computer-readable medium 908, such as a compactdisc-recordable (CD-R), a digital versatile disc-recordable (DVD-R),flash drive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 906. This computer-readable data 906, such asbinary data comprising at least one of a zero or a one, in turncomprises a processor-executable computer instructions 904 configured tooperate according to one or more of the principles set forth herein. Insome embodiments, the processor-executable computer instructions 904 areconfigured to perform a method 902, such as at least some of theexemplary method 300 of FIG. 3, at least some of the exemplary method500 of FIG. 5, and/or at least some of the exemplary method 700 of FIG.7, for example. In some embodiments, the processor-executable computerinstructions 904 are configured to implement a system, such as at leastsome of the exemplary system 400 of FIG. 4, at least some of theexemplary system 600 of FIG. 6, and/or at least some of the exemplarysystem 800 of FIG. 8, for example. Many such computer-readable media arecontemplated to operate in accordance with the techniques presentedherein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), electrically erasable programmable read-only memory(EEPROM) and/or flash memory, compact disk read only memory (CD-ROM)s,CD-Rs, compact disk re-writeable (CD-RW)s, DVDs, cassettes, magnetictape, magnetic disk storage, optical or non-optical data storage devicesand/or any other medium which can be used to store data.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard application orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer application accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, an application, or a computer. By wayof illustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method comprising: deleting data, associatedwith a composite aggregate, from a storage tier based upon a deleterequest; and performing an asynchronous object cleanup operation,comprising: sending a request to a remote object store, used to storeobjects comprising data of the composite aggregate, for a list of objectnames of objects having names associated with a volume identifier of avolume of the composite aggregate; and issuing delete commands to theremote object store to delete objects having object names within thelist of object names received from the remote object store.
 2. Themethod of claim 1, wherein a name of an object comprises a prefixderived from the volume identifier of a volume, of the compositeaggregate, to which the object belongs.
 3. The method of claim 1,wherein a name of an object is derived from the volume identifier and asequence number assigned to the object.
 4. The method of claim 3,comprising: assigning monotonically increasing sequence numbers toobjects created within the remote object store for a volume.
 5. Themethod of claim 1, wherein a name of an object is derived from a hash ofthe volume identifier and a sequence number assigned to the object. 6.The method of claim 1, comprising: storing a list of volume identifierswithin a cluster-wide database accessible to a plurality of nodes of astorage environment that hosts the storage tier but does not host theremote object tier that is hosted by a third party provider.
 7. Themethod of claim 6, comprising: deleting the list of volume identifiersfrom the cluster-wide database based upon objects associated with a setof volumes being deleted from the remote object store.
 8. Anon-transitory machine readable medium comprising instructions forperforming a method, which when executed by a machine, causes themachine to: delete data, associated with a composite aggregate, from astorage tier based upon a delete request; and perform an asynchronousobject cleanup operation, comprising: sending a request to a remoteobject store, used to store objects comprising data of the compositeaggregate, for a list of object names of objects having names associatedwith a volume identifier of a volume of the composite aggregate; andissuing delete commands to the remote object store to delete objectshaving object names within the list of object names received from theremote object store.
 9. The non-transitory machine readable medium ofclaim 8, wherein a name of an object comprises a prefix derived from thevolume identifier of a volume, of the composite aggregate, to which theobject belongs.
 10. The non-transitory machine readable medium of claim8, wherein a name of an object is derived from the volume identifier anda sequence number assigned to the object.
 11. The non-transitory machinereadable medium of claim 10, wherein the instructions cause the machineto: assign monotonically increasing sequence numbers to objects createdwithin the remote object store for a volume.
 12. The non-transitorymachine readable medium of claim 8, wherein a name of an object isderived from a hash of the volume identifier and a sequence numberassigned to the object.
 13. The non-transitory machine readable mediumof claim 8, wherein the instructions cause the machine to: store a listof volume identifiers within a cluster-wide database accessible to aplurality of nodes of a storage environment that hosts the storage tierbut does not host the remote object tier that is hosted by a third partyprovider.
 14. The non-transitory machine readable medium of claim 13,wherein the instructions cause the machine to: delete the list of volumeidentifiers from the cluster-wide database based upon objects associatedwith a set of volumes being deleted from the remote object store.
 15. Acomputing device comprising: a memory comprising machine executablecode; and a processor coupled to the memory, the processor configured toexecute the machine executable code to cause the processor to: deletedata, associated with a composite aggregate, from a storage tier basedupon a delete request; and perform an asynchronous object cleanupoperation, comprising: sending a request to a remote object store, usedto store objects comprising data of the composite aggregate, for a listof object names of objects having names associated with a volumeidentifier of a volume of the composite aggregate; and issuing deletecommands to the remote object store to delete objects having objectnames within the list of object names received from the remote objectstore.
 16. The computing device of claim 15, wherein a name of an objectcomprises a prefix derived from the volume identifier of a volume, ofthe composite aggregate, to which the object belongs.
 17. The computingdevice of claim 15, wherein a name of an object is derived from thevolume identifier and a sequence number assigned to the object.
 18. Thecomputing device of claim 17, wherein the machine executable code causethe processor to: assign monotonically increasing sequence numbers toobjects created within the remote object store for a volume.
 19. Thecomputing device of claim 15, wherein a name of an object is derivedfrom a hash of the volume identifier and a sequence number assigned tothe object.
 20. The computing device of claim 15, wherein the machineexecutable code cause the processor to: store the list of volumeidentifiers within a cluster-wide database accessible to a plurality ofnodes of a storage environment that hosts the storage tier but does nothost the remote object tier that is hosted by a third party provider.